Fuel injection in internalcombustion engines



Sept. 10, 1946. s MM 2,407,610

FEEL INJECTION IN INTERNAL-COMBUSTION ENGINE Filed Aug. 9, 1943 PatentedSept. 10, 1946 FUEL INJECTION IN INTERNAL- COMBUSTION ENGINES GeorgeStephen Kammer, Bradford, England Application August 9, 1943, Serial No.497,991

r In Great Britain March 16, 1942 4 Claims.

This invention relates to fuel injection in internal combustion enginesof the kind in which the fuel to be consumed in each cycle of eachcylinder is injected into the compressed air chargein two portions atsubstantially diiferent rates. It represents a further development ofthe invention described and claimed in my co-pending patent applicationNo. 403,722, filed July 23, 1941.

In the patent application mentioned reference was made to the use of arather large volume or capacity between the pumping space and theinjector needlevalve leading to the jets for the primary or pilot rateof injection, and it was proposed to make use of the compressibility ofthe fuel for limiting th maximum pressure due to the restricteddischarge area in connection with a single or steady cam lift for thepump plunger.

That method is quite satisfactory in cases where (a) the pump plunger isnot called upon to perform more than about 1000 injections per minute,and (b) where the pump unit is located rather far away from the nozzlesand the capacity can be so formed that it acts as a trap, so to speak,for the ram effect induced in the pipes during operation, but it isdifilcult to provide for in other cases.

It is an object of the invention to provide a fuel pump for high speedoperation in which the maximum pressure is so limited.

A further object of the invention is to provide a fuel pump combinedwith the injection nozzles in which the maximum pressure is so limited.

Another object is to provide means by which the crank angle during whichpilot injection is to take place may be predetermined more or lessindependently of the amount to be injected during this crank angle.

Yet a further object of the invention is to provide limited leakage ofthe fuel into the pump suction space during pilot injection to restrictthe quantity and pressure of the fuel.

Other objects will appear from the following description of a pump andnozzle combination shown in the accompanying drawing, in which Figure 1is a central longitudinal section through the combination,

Figure 2 is a transverse section taken on the line II-II of Figure 1,and

. Figure 3 is a central longitudinal section on the line Ill-III ofFigure 2, that is at right angles to the section of Figure 1.

Referring to the drawing, a pump cylinder I contains a pump plunger 2,in which a groove 4| is shaped to vary the timing of port opening as 2disclosed in my co-pendin'g, patent application No. 403,722, filed July23, 1941. Fuel is supplied through a duct 3 to an inlet trunk 4 formedas a portion of an annulus on the outer surface of the pump cylinder I,which may be sealed by a sleeve 5. The pressure space 6 of the pump isin direct communication with the trunk 4 through a, port i when theplunger 2 is in the uppermost position as shown, but this communicationis interrupted when the plunger has moved a short distance downwards.

Two outlet leads 8 and 9 are connected to the pressure space 6, of which8 is always open and provides the pilot fuel, while 9 is controlled asto opening and closing by movement of the plunger 2 over an outlet port9 and provides the main charge of fuel. These outlet leads 8 and 9convey the fuel to the pilot fuel jet l2 and the main fuel jet l3respectively through check valv loaded by springs 10.

The plunger 2 has a head 42, which is embraced by the lower end of atappet 45, so that the plunger positively follows the movements of thetappet. The upper end of the tappet 45 slides in an upward extension 36of the pump cylinder l and is urged upwards by a plunger return springH, which bears on a shoulder 43 of the tappet 45 and an inward flange 31of the extension 36. An actuating cam- H! on the camshaft 2t bears on amushroom 2| formin a part of the tappet 45.

For rotating the plunger 2 to bring different parts of the helical edgeof the groov 4i into operation and so to vary the quantity of fuelinjected, there is provided a gear wheel 24 Which may be integral withthe plunger 2 and is located to engage a rack 25. The rack teeth arewide enough to retain engagement with the gear wheel 24 at all positionsof the plunger 2 in its working stroke. The rack bar 25 is of roundsection at the part away from the teeth and is adapted to slide in asuitably machined recess in the pump body I to adjust the quantity offuel delivered at each pump stroke. i

A small port 32, which I propose to call a control orifice, is locatedin the pumping space 6 to be covered by the pump plunger and so closedat a certain point in the stroke. There may also be a check valve 33loaded by a spring 34 and located in a bore sealed by a plug 35. Thisvalve in its closed position closes the passage leading from the controlorifice 32 to the inlet trunk 4. The check valve 33 has axial grooves(not shown) to permit fuel from the trunk 4 to pass to the spaceoccupied by the spring 34 and vice versa,

orifice 32 into the inlet trunk 4' either directly or, if th optionalcheck valve 33 is provided, by lifting the same from its seating.

The orifice 32 is so located that the inward edge of the plunger 2passes over it just as the helical edge of the plunger uncovers the port9 Hereafter discharge can only take place through the jets l2 and it,that is both the pilot and-the main jets. Ehus a quantity of fuelexactly corresponding to the displacement of the pump plunger 2,according to cam lift, is, in its entirety,

discharged into the engine combustion space.

Obviously, by varying. the size and shape of the control orifice 32,various amounts of pilot fuel can 'be arranged to be discharged into theengine combustion space. Also it is clear that more fuel is injectedthrough the combined discharge of jets l2 and I3 than by jet or jets l2alone, whilst some of the fuel-displaced by the plunger 2 is beingdischarged into trunk 4.

12 may for example be one jet of .010" diameter for the pilot fuel and13 may be four jets of similar size for the bulk or main fuel. Then thecontrol orifice 32 should be so dimensioned that it discharges an amountof fuel substantially similar to that discharged by the four jets formain injection. This does not necessarily mean a similar totalcross-sectional area, for the friction of the fuel, the capillarity ofthe orifices and the pressure difference between the trunk 4 and theengine combustion space must be taken into account.

If it is desired to inject the pilot fuel at higher pressure than themain fuel, the discharge characteristics of the control orifice 32 mustbe modified accordingly.

In such arrangements the pilot injection and the main injection vary indifferent ways with speed owing to several factors. Some of the factorsare the rise of injection pressure and the rise of compression pressurein the engine cylinder with rising speed, the constancy of fueladmission pressure and the variation of the volumetric efficienc of thepump. The check valve 33 can be arranged to alter the dischargecharacteristics in the desired manner.

It is also possible to arrange, within thecylinder or body i acontrollable check valve, which is in continuous communication with thespace 2.

This check valve could be coupled with the plunger 2 in such way thatthe rotation of the plunger 6 would also rotate the check valve,preferably a needle-valve having a thread, and thus vary the areathrough which continuous discharge would take place from the space 6during injection. At low speeds the area would be considerablyrestricted, at high speeds increased.

It is in most cases desirable during starting that no pilot fuel shouldreach the engine cylinder, as such fuel cannot be burnt within theecessary short time owing to lower compression of the air charge in acold engine. With a pump of the kind'now described the start position ofthe pump plunger is one which will give injection during a considerablylarger proportion of the pump stroke than at full load and is notutilised during normal operation of the engine.

d- It is thus possible to cut away the top edge of the pump plunger 2for a portion of the circumference corresponding to the start positiononly. While in normal running injection commences well before the innerdead centre, this arrangement will confine injection during starting tothe main fuel and shift the commencement of injection to a pistonposition near the inner dead centre, because the cut-away portionensures that the pumping space is not closed until the orifice for themain injection is uncovered by the plunger. Such provision will greatlyassist in starting.

What I claim is:

l. A fuel injector for an internal combustion engine of the kind inwhich fuel to be consumed in each working cycle is injecteduninterruptedly into a compressed air charge in two portions, namely apilot fuel portion and an immediately following main fuel portion, thetwo portions being injected at substantially different. rates,comprising a jerk type pump having a cylinder formed with a compressionspace, a plunger operable in said compression space, a fuel inletpassage terminating in an inlet port in the wall of the compressionspace at a part traversed by said plunger, a first outlet from thecompression space out of reach of the plunger for the pilot fuel, asecond outlet from the compression space. separate from said firstoutlet and having an outlet port opening into the compression space wallat a part thereof traversed by the plunger for discharging the main fuelportion, a groove in the plunger located to uncover said-outlet port andsaid inlet port in succession during the working stroke of said plunger,and a control orifice in the wall of said compression space separatefrom said outlet and being located to be covered by said plunger duringthe latter part of said working stroke and being adapted to dischargefuel from said compression space.

2. A fuel injector for an internal combustion engine of the kind inwhich fuel to be consumed in each working cycle is injecteduninterruptedly into a compressed air charge in twoportions, namely apilot fuel portion and an immediately following main fuel portion, thetwo portions being injected at substantially different rates, comprisinga jerk type pump having a cylinder formed with acompression space; aplunger operable in said compression space, a fuel inlet passageterminating in an inlet port in the wall of the compression space at apart traversed by said plunger, a firstoutlet from the compression spaceout of reach of the plunger for the pilot fuel, a

second outlet from the compression space separate from said first outletand having an outlet port opening into the compression space wall'at apart thereof traversed by'the plunger for discharging the main fuelportion, a circumferential groove in the plunger located to uncover saidoutlet port and said inlet port in successiondur- "ing the workingstroke of said plunger, and a control orifice in the wall of saidcompression space separate from said outlet and being located to becovered by said plunger during the latter part of said working strokeand commu- 3. A fuel injector for an internal combustion engine of thekind in which fuel to be consumed in each working cycle is injecteduninterruptedly into a compressed air charge in two portions, namely apilot fuel portion and an immediately following main fuel portion, thetwo portions being injected at substantially different rates,

comprising a jerk type pump having acylinder formed with a compressionspace, a plunger operable in said compression space, a fuel inletpassage terminating in an inlet port in the wall of .the compressionspace at a part traversed by said space separate from said outlet andbeing located between said ports and said first outlet so as to remainuncovered by said plunger during the first part of the plunger workingstroke and to then be covered by said plunger during the latter part ofthe plunger working stroke when said outlet port is uncovered by saidcircumfer ential groove, said control orfice communicating with saidintake passage.

4. A fuel injector as set forth in claim 2 including a check valveinterposed between said control orifice and said inlet passage and beingarranged to open towards said inlet passage in:

response to pressure in said control orifice.

GEORGE STEPHEN KAMMER.

